1. Field of the Invention
The present invention relates to a document processing apparatus and, more particularly, to the alignment and test of sensors within the document processing apparatus.
2. Prior Art
Referring to FIG. 1, there is shown a perspective view of a document processing apparatus 10. The apparatus 10 could be any suitable type of document processing apparatus, such as a copier, a facsimile machine, a scanner, a computer printer, or a multifunction device having two or more functions. Referring also to FIG. 2, in this embodiment the apparatus 10 is a copier which includes an original document feed system 11 and a copy document feed system 13. A scanner or image obtainer 12 is provided under a transparent glass platen 15. The scanned information from the scanner 12 of information on an original document fed through the original document feed system 11 is imaged onto paper selected from paper trays 14 or 16. Paper selected from either of the paper trays 14,16 is moved by the copy document feed system 13 through the apparatus 10 by means of various belts 18 and rollers 19 schematically depicted in FIG. 2. The original document feed system 11 also comprises suitable belts and rollers. Throughout the paper paths of the two feed systems 11,13 there are mechanical sensors 30,50 and optical sensors 20,40 to indicate where and when a piece of paper is located. The sensors are initially aligned and tested during manufacture and re-aligned and tested as required by field service technicians throughout the life of the apparatus.
In the case of optical sensors 20,40 the sensors are aligned so that when paper is present, light from a light emitting diode 20a,40a encased within the sensor is blocked by the paper from the photosensitive transistor 20b, 40b, respectively, also encased within the sensor. Similarly, in the case of mechanical sensors, the sensors 30,50 are aligned so that when paper is not present the switch 30a,50a, respectively, is closed, thus, indicating the non presence of paper.
During manufacture the mechanical sensors may be aligned or tested using elaborate mechanical setups such as special mechanical jigs, or in the case of optical sensors, a cumbersome digital voltmeter and a power supply arrangement may be used. However, the slow response time of the digital voltmeter leads to a tedious and repetitive alignment process for each sensor being aligned. Moreover, the slow response time and unbuffered sensor signals can also lead to misaligned sensors requiring later apparatus disassembly if still in manufacture or alignment by a field service technician if the unit is in service.
Diagnostic programs within the document processing apparatus exist for assisting a field service technician in aligning and testing a sensor but require that the technician be able to see the apparatus screen or display 8 (see FIG. 1). However, many of the sensors are located such that the technician cannot see the display 8 while aligning or testing a particular sensor. Thus, attempting to align or test a sensor by use of the display 8 is awkward and time consuming.